Safety and Efficacy of Tivozanib in First-Line mRCC: A Multicenter Compassionate-Use Study (Meet-Uro 16)

Introduction: Tivozanib is a potent and selective tyrosine kinase inhibitor of vascular endothelial growth factor receptor 1 (VEGFR-1), VEGFR-2, and VEGFR-3, recently approved in Europe for the first-line treatment of metastatic renal cell carcinoma (mRCC). Methods: Retrospective analysis of safety and activity of tivozanib administered at 1.34 mg daily (3 weeks on, 1 week off) within a compassionate-use program to patients with mRCC with no prior systemic treatment in Italy. Results: From August 2018 to April 2019, 64 patients have started tivozanib in 9 oncology units. The median age was 67.5 years (range 40-85), 62.5% males. According to International Metastatic Renal Cell Carcinoma Database Consortium criteria, 27.1% of patients were good prognosis, 57.6% intermediate, and 15.3% poor. Primary tumor had been removed in 71.9% of patients. Histology was clear cell 89%, papillary 4.7%, and unclassified 6.3%. The response rate was 34.4%, stable disease 40.6%, and progression 15.6%. Grade 3-4 toxicities were 7.8% hypertension, 4.7% anemia, 3.1% mucositis, 3.1% asthenia, 1.6% diarrhea, 1.6% anorexia, 1.6% worsening of renal function, and 3.1% cardiac events. Dose reduction to 0.89 mg was applied to 17.2% of patients, and the discontinuation rate due to toxicity was 5.8%. Median progression-free survival was 12.4 months, with 68.7% of patients alive at 12 months. The developing of hypertension predicted increased progression-free survival at multivariate analysis (HR, 0.128; 95% CI, 0.03-0.59; p = 0.008). Conclusions: Tivozanib showed good activity and favorable safety profile in a real-world cohort of unselected patients with mRCC. Predictive biomarkers of response to antiangiogenic therapy are urgently needed in order to identify RCC patients who could still receive a monotherapy with VEGFR inhibitors in the first line.